The present invention relates to a side airbag apparatus that inflates and deploys an airbag beside at least the thorax of an occupant seated in a vehicle seat to reduce an impact applied from the side, thereby protecting the occupant. More specifically, the present invention pertains to a side airbag apparatus that has an airbag with a thickness limiting portion at a part corresponding to an arm of an occupant, and is configured to prevent the arm from being pressed toward the thorax by the airbag.
A side airbag apparatus is widely known that includes an airbag and an inflator and protects an occupant when an impact is applied to a vehicle from a side due to a side collision. In such a side airbag apparatus, the airbag is formed by stacking a pair of fabric portions along the widthwise direction of a vehicle (vehicle widthwise direction) and joining the fabric portions to form a bag-like shape. The inflator is arranged at the rear end of the airbag. After being folded into a compact form for being accommodated, the airbag, together with the inflator, is incorporated in a seat back of a vehicle seat. In the side airbag apparatus, when an impact is applied from the side of a body side portion, such as a side door, of a vehicle, the inflator discharges gas into the airbag. The discharged inflation gas inflates and deploys the airbag forward from the seat back into a narrow space between the occupant seated in the vehicle seat and the body side portion, so that the airbag reduces impact applied to the occupant from the side through the body side portion.
In the side of the human body, lumbar regions are generally known to have a better impact resistance than the thorax. Thus, if, during the inflation and deployment, an airbag pushes an arm of an occupant inward in the widthwise direction of the vehicle seat (toward the thorax), the thorax, which has a relatively low impact resistance, might be pressed by the arm.
In this respect, for example, Japanese Laid-Open Patent Publication Nos. 2008-184159 and 2009-001057 each disclose a side airbag apparatus that has an airbag with a thorax protecting portion for protecting the thorax of an occupant. The thorax protecting portion includes a thickness limiting portion at a part corresponding to an arm of the occupant. The thickness limiting portion is formed by connecting the fabric portions to each other at a position corresponding to an arm of the occupant, while bringing the fabric portions in contact with or close to each other. According to the side airbag apparatus having such a thickness limiting portion, the thickness of the thorax protecting portion along the widthwise direction of the vehicle seat is limited at a position where the thickness limiting portion is provided. It is therefore unlikely that the arm is pressed by the thorax protecting portion and pushes the thorax.
In the above side airbag apparatus, it is preferable that the thorax protecting portion of the airbag be quickly inflated and deployed forward from the compactly folded accommodation state, thereby protecting the thorax of the occupant from an impact at an early stage. Since it is located on the path of the flow of inflation gas from the inflator, the thickness limiting portion adversely influences the deployment and inflation of the thorax protecting portion at an early stage. However, the prior art disclosed in Japanese Laid-Open Patent Publication Nos. 2008-184159 and 2009-001057 does not take such adverse influence into consideration.